CH670447A5 - - Google Patents

Description

DESCRIPTION

The present invention relates to a device for the formation by pyrolysis of a coating of metallic compound on the upper face of a hot glass substrate in the form of a sheet or ribbon, comprising transport means for conveying such a substrate to the downstream along a route, a treatment station comprising a roof delimiting a chamber open downwards on said route and means for spraying a coating-forming solution in said chamber, downwards and towards the substrate. The invention also relates to a process for the formation by pyrolysis of a coating of metallic compound on the upper face of a hot glass substrate in the form of a sheet or ribbon during its downstream travel along a through a chamber in which at least one stream of coating forming solution is sprayed downward and towards the substrate.

Such devices and methods are useful for making glass with coatings for different uses; the coating is chosen to give the glass particular properties. Especially important examples of coatings which can be applied to glass are those intended to reduce the emissivity of the face carrying the coating with respect to infrared radiation, especially infrared radiation having wavelengths greater than 3 | im, and those intended to reduce the total energy transmission factor of the glass bearing the coating with respect to solar radiation. It is known, for example, to provide glass with a coating with low emissivity with respect to infrared consisting of tin dioxide, to conserve heat, and it is also known to provide glass a coating reducing the solar energy transmission factor consisting of a metal oxide such as titanium dioxide or a mixture of metal oxides such as Fe203 + CoO + Cr203, the main purpose of which is to reduce the calorific intake due in the sun or glare.

It is obvious that coatings applied to glass intended for glazing must have a high and uniform optical quality. Because the coatings are usually applied in thicknesses between 30 nm and 1200 nm, depending on the nature of the matrix constituting the coating and the properties required, variations in the thickness of the coating can give rise to interference effects. detrimental and therefore uniform thickness is important for good optical quality. However, it is also particularly important that the coatings are free from stains or other localized defects and that they have a regular and uniform crystal structure.

In any case, it is not easy to form, by pyrolysis, coatings which have uniformly good optical quality, particularly at fairly high deposition rates, such as those required to form thick coatings on rapidly moving glass substrates, for example a coating of tin oxide 750 nm thick on a freshly formed ribbon of float glass moving at more than 8 meters per minute. Uniformity in thickness, composition and / or structure are very likely to appear in an industrial-scale coating installation and a great deal of research has been devoted to finding a solution to this problem.

Such research has explored the possibilities of using devices to implement two coating deposition techniques, namely deposition from vapor-phase coating formative material and deposition from liquid-phase coating formative material .

In the case of vapor deposition, research has led to a technique in which vapor coating coating forming material is introduced into a chamber and it is made to flow in a regular, well-controlled, non-turbulent current. and uniform in contact with the substrate to be coated. However, although we have found that this technique can result in the formation of a thin and uniform sutructure coating, we have not been

even to obtain a satisfactory regularity of thickness, compatible with commercial requirements, especially for large glazing, such as modern architectural practice demands it more and more. It has simply been impossible to construct devices which allow the desired degree of control to be exercised over the introduction of the coating formative material into the chamber so that it flows uniformly and regularly in contact with the glass when operates on a commercial scale; as a result, unpredictable variations in thickness are present in the coatings formed and a certain proportion of coated glass produced is not of acceptable quality. In addition, it is necessary to use a fairly volatile coating forming material, and this represents an undesirable limitation in the choice of available reagents. In addition, known vapor coating methods do not readily lend themselves to the formation of a coating having a thickness greater than 400 nm, especially when the glass has to move quickly enough to meet the criteria of use of other installations used. in the industrial production program.

In order to form thick coatings, it is usual to use a liquid or spray coating device to spray a stream of droplets of coating formulator solution onto the substrate. Such a device simplifies the handling of large quantities of coating formative material required, but it has certain disadvantages. First, there is a significant risk that contact between the usually fairly large amounts of sprayed coating solution and the hot glass substrate will give rise to steep thermal gradients inside the glass, and as a result, when of the cooling which follows the coating operation, high stresses settle in the glass. This can make it very difficult to cut the glass into sheets or smaller sheets if necessary, and makes the glass easily brittle. Then, it is very difficult to obtain a high quality and uniform coating.

In the search for quality improvement, attention was first focused on the conditions in and in the immediate vicinity of the area where the sprayed matter droplets reach the glass. Coating defects are very likely to occur in this region due to entrainment of reaction products contained in the gaseous environment by the stream of spray droplets, or due to splashing of the droplets upon impact on the glass. In order to avoid such faults, various proposals have been made, including the generation of gas streams to sweep the potentially harmful material out of the atmosphere located in the immediate vicinity of the impact zone. In a known method, a continuous ribbon of glass is conveyed through a chamber where a solution of coating formative material is sprayed by a spray head driven in a back and forth movement. The spray head is controlled so as to obtain a stable supply of droplets to the impact zone and a sweeping gas stream is blown along the glass through this chamber, so as to clean the atmosphere in this transverse path , ahead of the stream of droplets. The purge gas stream can be continuous and, in this case, it inevitably reaches the stream of sprayed droplets. However, in this case, care is taken to reduce the speed of the gaseous sweeping current so that it does not disturb the conditions of continuity and stability at the impact zone.

The continuous and regular supply of droplets required is conditioned by a sufficiently low spray energy. For this reason, the use of this device is limited as regards the quantities of coating which can be formed in a given time (coating formation rate).

In order to form good quality coatings more quickly, it has been proposed to use a much higher energy spray and simultaneously blow strong gas streams against and around the stream of spray droplets in the vicinity of the area. impact so that the droplets that

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splashing and bouncing glass will be immediately entrained. Although the formation of higher amounts of coating in a given time (coating formation rate) is possible by this method, to avoid the formation of defective coatings resulting from splashing of the droplets, it is necessary that the nozzle (s) blowing of the purging gas are very carefully directed and controlled. The purge gas must be supplied by nozzles which are closely associated with the spray head and move in solidarity with it along its transverse path. When using this high energy sputtering process, glass is particularly susceptible to high stresses, and it has further been found that the coating can contain defects at an unacceptable frequency, even after the most careful adjustments of the spray head and associated purging gas blast nozzles.

We have found, when using the known spraying device, despite careful control of the spraying environment, that the coatings often do not have the structural characteristics necessary for high optical quality and that it is difficult to to obtain these characteristics in a safe and reproducible manner, the difficulty being all the greater the higher the expected coating rate. In particular, we have found that the resulting coatings have a high haze and, which is more detrimental, that this haze is irregular on the surface of the coating.

One of the objects of the present invention is to provide a device capable of forming coatings of high optical quality and of uniform structure in a safe and reproducible manner, even at high coating formation rates, and without inducing high thermal stresses in the glass substrate.

The present invention provides a device for the formation by pyrolysis of a coating of metal compound on the upper face of a hot glass substrate in sheet or ribbon form, comprising transport means for conveying such a substrate to the downstream along a route, a treatment station comprising a roof delimiting the chamber open downwards on said route and means for spraying a coating-forming solution in said chamber, downwards and in the direction of the substrate, characterized in what:

- The spraying means are arranged so as to spray said formaric coating solution in a spraying zone of said chamber from a height of at least 75 cm above the path of the substrate;

- Heating means are present and supply heat to said spraying zone;

The roof delimits a portion of said chamber forming a passage downstream from said spraying zone and giving the chamber a total length of at least 2 meters, and

- Means are present for generating suction forces acting on the atmosphere located inside the passage by promoting the flow of the material which constitutes it along the path of the substrate towards the downstream end of said passage and the penetration of the latter into a drainage pipe which moves it away from the path of the substrate.

A device according to the invention is more economical to use than a traditional vapor-phase coating device, in which the coating-forming material must be vaporized before coming into contact with the glass, and it is of more construction. simple than known spraying devices, in particular because it avoids the problems associated with splashing and entraining large sprayed amounts of coating formulator solution outside the area where the coating is formed.

When using a device according to the invention as described above, it has been found that it is much easier to safely and reproducibly form coatings of high optical quality and of uniform structure, even at rates of high coating formation and without inducing high thermal stresses in the glass. In particular, it has been found that it is much easier to obtain coatings with little haze, and the latter being uniformly distributed.

Obviously, in order to obtain such a high reproducible quality of coating, the device must be used appropriately, but the combination of characteristics of the device as described above is particularly advantageous for facilitating the control of the conditions inside. bedroom. It has been found that, to obtain these good results using the device, it is preferable to control the deposition conditions so that a substantial proportion of the coating formulator solution is evaporated before it comes into contact. with the substrate, such that the atmosphere in the spraying zone is charged with vapor of coating formative material which is then taken along the passage where it covers the substrate and remains in contact with it.

In fact, this represents an entirely different orientation from the teaching of prior techniques in this area. Hitherto it has been believed necessary to control the deposition conditions so that as little coating formative material as possible is vaporized, so as to prevent it from reacting with the atmosphere within the zone of spraying and does not form reaction products which could deposit on the substrate and form defects on the coating. It has also been found necessary to vacuum excess coating formative material and reaction products from the substrate environment as soon as possible, again to avoid harmful deposits on the substrate, and lengths of coating areas of the substrate. 60 cm to 100 cm are typical in prior techniques.

The reasons why using such a device promotes better coating quality standards are not entirely clear, but the fact is that with the help of such a device one is able to produce coatings of which the veil is more uniform and weaker than has been possible before. The coatings formed can have a high optical quality and a regular and predictable thickness. In addition, by the use of such a device, these coatings can be formed more quickly on glass substrates, and therefore fabricate thicker coatings or on substrates which move faster than has been possible until now. now.

A particularly important use of a device according to the invention is the formation of a coating of tin oxide from stannous chloride as a coating-forming material. Tin oxide coatings, which reduce the emissivity to long wavelength infrared radiation from the glass sheet surfaces on which they are deposited, are widely used to reduce the heat transmission of structures glazed. This, of course, is only an example of the destination of the device. As another example, the device can be used to form a coating of titanium dioxide or a mixture of oxides such as a mixture of cobalt, iron and chromium oxides.

The device is particularly advantageous for quickly forming coatings, as is for example necessary for forming relatively thick coatings, for example a coating of 500 nm to 1000 nm thick, on a freshly formed glass ribbon moving from several meters per minute from a float tank or other flat glass forming installation.

Preferably, the chamber has a length of at least 5 meters. It has been found that this arrangement is particularly advantageous for the formation of relatively thick coatings, for example those with a thickness of 500 nm or more, because, for a given speed of movement of the substrate, it allows a longer contact time between the coating forming material vapor and the substrate, for depositing additional coating forming material and / or conditioning the already deposited material.

In specially preferred embodiments of the invention, the spraying means are arranged to spray said coating forming solution from a source located

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at least 1 meter, and preferably at least 1.2 meters, above the path of the substrate. This allows a long path of the sprayed material, which gives more time for the evaporation of this material before it comes into contact with the glass, and involves a high spraying area which can thus serve as a reservoir for evaporated material from which this material is extracted downstream towards the interior of the passage. A device comprising this preferred characteristic can be opposed to the previously known devices in which a spraying height of 30 cm or less is usual.

In specially advantageous embodiments of the invention, at the downstream end of the spraying area, the roof descends substantially vertically to delimit an outlet slot leading to said passage. This provides very significant benefits. The reservoir effect in the spraying area is improved, so that it is easier to extract material from the atmosphere which is uniformly charged with vapor of coating formative material and to bring it towards the inside the passage and, moreover, that the vapor-charged atmosphere is forced to flow downward towards the substrate.

Preferably, the height of said outlet slot is at most equal to half the height between the spray source and the path of the substrate. This has been found to provide room for a good mixture of material from the atmosphere in the upper half of the spray area not in line with the outlet slit, and further promotes the uniformity with which the atmosphere can be charged with vapors of coating formative material.

Advantageously, over at least part of its length, the passage has a height less than that of the spraying zone. Atmospheric material flowing along such a lower passage is thereby forced to flow relatively close to the substrate, so that the vapor of coating formative material entrained therein can act on the coating.

In certain preferred embodiments of the invention, the roof converges downstream in the direction of the path of the substrate over the length of said passage. This improves the downward accumulation of material from the atmosphere inside the passage, despite the decrease in the volume of this material during its movement in the downstream direction.

In other preferred embodiments of the invention, the roof has a wall above the path of the substrate which delimits an exit slot from the spraying zone and which separates this zone from said passage, this passage having a height more larger than that of the exit slot. In such constructions, air currents entering the passage from the outlet slot will naturally slow down, and it is possible to rely at least in part on the high density of the coating formant vapors to keep them in contact with a substrate moving through the device.

In especially advantageous embodiments of the invention, the spraying means are arranged so as to spray the coating forming material downward and in the downstream direction. This promotes the distribution of the coating forming material while maintaining a general downstream flow in the chamber, lengthens the trajectory of the sprayed material by comparison with a vertical spraying from the same height thereby lengthening the evaporation time of the solution, and facilitates the placement of heating means in the spraying area so that they have an effect on the sprayed material.

Preferably, means are present for delivering coating formative material and at least one gas stream into said spraying zone in intersecting directions. This constitutes a very simple means of ensuring the mixing of the materials which will be introduced into the spraying zone during the use of the device, without the need for a special mixing device which should be able to withstand the hot and corrosive atmosphere generated. in this area.

Advantageously, there is at least one device for delivering gas having an orifice disposed in the upper half of the height between the spray source and said substrate face. The use of such a device is very effective in promoting mixing without disturbing the atmosphere too much immediately above the path of the substrate.

In specially preferred embodiments of the invention, means are present for preheating at least one such gas stream. This prevents condensation of the sprayed material. It is desirable to avoid condensation of coating formant vapors on the walls and ceiling of the chamber, as this will cause corrosion and run the risk of condensed material drip onto a substrate and soil a coating form.

In certain preferred embodiments of the invention, at least one device for delivering gas is arranged so as to discharge such a stream of gas from a location located upstream of the spray axis of coating formative material. The supply of gas by such means promotes good circulation of gas streams inside the chamber.

Preferably, downwardly directed radiation heating means are placed above the spray area. This is a very simple way to provide heat to evaporate the sprayed coating solution. Such heating means are also useful for increasing the temperature in the spraying area so that the formation of the coating can at least start at higher temperature, which is advantageous for the performance and durability of the coating and prevents condensation on spray area ceiling.

Preferably, means are present for heating said passage from above. Such heating means are useful for increasing the temperature inside the passage so that the coating is finished and conditioned at a higher temperature, which is advantageous for the hardness and durability of the coating formed and prevents condensation on the ceiling. of the passage.

In certain preferred embodiments of the invention, upstream of the spraying axis of the means for spraying the coating forming material, means are present for discharging a gas jet downwards in the vicinity of said spraying axis, so as to protect the spray coating formative material. This helps to avoid entrainment of any unwanted material, for example reaction products, in the rear part of the stream.

Preferably, the means for spraying coating formative material comprise a spray nozzle and means for repetitively moving such a nozzle along a path transverse to the path of the substrate. This promotes mixing of the evaporative coating material in the atmosphere of the chamber spray area.

Means are advantageously present for repetitively moving the means for discharging a jet of protective gas along a path transverse to said path of the substrate in tandem with the spray nozzle of coating formative material. This allows effective protection of the spray while introducing relatively low qualities of shielding gas.

In certain preferred embodiments of the invention, means are present for blowing gas upwards on each side of the path of the substrate in the spraying zone. Such blowing means can be used to form gaseous screens against the side walls of the spray zone of the chamber which serve to protect these walls against the corrosive effects of the sprayed material and its reaction products. Such gaseous shields can also prevent the sprayed material, particularly when relatively small amounts are sprayed, from passing below the path of the substrate where it could form an undesired coating on the underside of a substrate.

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Preferably, a discharge pipe is arranged at the downstream end of said chamber and has one or more inlets arranged above the path of the substrate and extending through at least most of its width. Such an evacuation pipe is of simple construction and is very easy to place, and it allows efficient material suction outside the path of the substrate. The use of such a pipe is particularly well suited to entrain the material sucked substantially in the downstream direction until it enters the pipe, which brings a minimum of disturbance of the flow inside the passage. Adopting this feature is highly desirable when large amounts of coating formulator solution are sprayed into the chamber.

A curved shovel is advantageously present at such a discharge inlet. It has been found that this arrangement allows a very efficient suction of reaction products and unused coating formative material, since such material from the atmosphere can flow regularly inside the evacuation pipe. This has very important practical advantages, especially when forming relatively thick coatings, for example to form a tin oxide coating of reduced emissivity. It is preferred that this discharge shovel be movable to adjust the day between its base and the path along which the glass moves, for example by means of a pivoting assembly, so as to close as much as possible the downstream end of the bedroom.

Depending on the pressure conditions prevailing above and below the substrate in the chamber, the atmosphere laden with coating forming material may tend to flow below the substrate where it will deposit an undesired coating on its underside . Depending on the profile of atmospheric currents in and below the chamber, this undesirable coating can be more or less regular and so thin that it gives rise to highly detrimental interference effects; for example, it can be a more or less regular coating whose thickness decreases towards the center of the substrate, or it can be a fairly irregular coating with a profile which could recall the marks of a backgammon game. This tendency is to some extent inhibited by the placement of upwardly directed blowing means on the sides of the spray area as described above. Alternatively, however, material from the atmosphere may tend to flow upward from below the path of the substrate and dilute the vapor concentration of coating formative material, especially on the sides of the chamber. This is undesirable, since it can lead to the formation of a coating from the insufficient vapor phase on the margins of the substrate or to insufficient conditioning of the margins coated with such a substrate; consequently, in particularly advantageous embodiments of the invention, means are present to prevent the flow of material from the atmosphere beyond the lateral edges of the path of the substrate and between zones situated vertically above and vertically below this path, over at least part of the length of the chamber.

Preferably, the means for preventing the flow comprise deflectors, which constitutes a very simple way of obtaining the desired result. Such deflectors can be arranged so as to create a substantially closed chamber, and so that the atmosphere inside is not affected by external gas streams. A very simple and preferred way of obtaining a substantial closure is to choose conveyor rollers having a zone of smaller diameter at each edge of the path of the substrate so as to delimit a space which adapts to said deflectors between the rollers and the edges the path of the substrate. This allows the entire upper face of the substrate to be coated.

We have mentioned the placement of an evacuation pipe across the path of the substrate at the downstream end of the passage of the chamber. However, having the means to exert suction forces at this single location can give rise to a higher concentration of vapor of coating formative material along the center of the passage than at the edges of the path of the substrate. This is another possible cause of unsatisfactory coating of the edges of the substrate. In order to reduce this tendency and to increase the useful width of the coated substrate, it is especially preferred that means are present for generating suction forces in a lateral evacuation pipe arranged so as to make it deviate from the material the atmosphere surmounting the path of the substrate from the center of said path, over at least a portion of said passage. The adoption of this preferred characteristic gives advantages which are considered to be particularly important. It promotes good dispersion of the atmosphere loaded with coating forming material over the entire width of the substrate, thereby increasing the finished width of the coating of the substrate. It is also useful for removing excess coating formers and reaction products before they reach the end of the passage, thereby reducing the risk of corrosion of the walls of this passage. In addition, it allows the removal of reaction products and excess coating formative material which could become fixed on the coating and dirty it. In addition, if the atmosphere below the path of the substrate tends to flow upwards beyond its edges, this tendency is inhibited on the lateral suction zone. These advantages are increased if, as is preferred, said evacuation pipe is arranged so as to suck material from the atmosphere, laterally, over an area extending substantially over the whole of said passage.

In certain preferred embodiments of the invention, said lateral evacuation pipe has inlets which are arranged below the level of travel of the substrate. This arrangement is advantageous because it facilitates the visual control of the conditions inside the passage through openings which can be made in its side walls and, in use, it facilitates the finishing of the coating by holding against the face of the substrate which is coated with a layer of dense vapors of coating formative material.

One cause of defects in a coating formed by pyrolysis is due to particles of foreign matter which can be incorporated into the coating during its formation. During the coating operation, the chamber takes up unused coating formative material and reaction products, including intermediate reaction products. It should be noted that these products and other pollutants such as dust (the coating-forming material is itself considered to be a pollutant wherever it can come into contact with hot glass, except in the chamber) tend to spread towards upstream from the chamber in which the coating forming material is discharged, as small as the opening for entry of the glass into this chamber, and, in fact, these pollutants can come into contact with the glass before it does not reach the coating area and form harmful deposits on the substrate, remain there and be incorporated into the coating as defects, for example at the coating / glass interface or in the thickness of the coating.

Advantageously, means are present for discharging gas into the environment of the substrate, so as to form a direct current flowing downstream, below each edge of the path of the substrate and along at least part the length of the course occupied by said chamber.

Surprisingly, it has been found that the use of a device incorporating this preferred characteristic has the result of significantly clarifying the atmosphere which would be in contact with the glass before it enters the chamber, so that there has a considerable reduction in the quantity of pollutants capable of forming harmful deposits on the glass before it is coated.

A possible explanation for this phenomenon is as follows.

Upstream of the chamber, there will be an installation for heating the glass substrate or for forming the hot glass substrate and, downstream of the chamber, there will usually be means such as, for example, an annealing gallery, allowing cooling con5

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controlled by the substrate carrying the coating. In such constructions, there may be a material return current from the atmosphere which flows in the upstream direction below the path of the substrate. This return current which flows upstream can rise above the path of the substrate, so that pollutants entrained by it are liable to be deposited on the substrate, forming defects embedded in the coating.

The use of a device having this preferred characteristic of the invention also offers certain very important advantages for the quality of the product, by reducing the risk of coating formation on the underside.

These advantages are increased if, as is preferred, the means for discharging gas to form such a current below the level of the path of the substrate are arranged so as to discharge gas to form such a current across the width total path of the substrate.

Preferably, means are present for preheating the gas to be discharged to form such a current below the level of the substrate, for example up to fifty degrees Celsius of the average temperature of the substrate immediately before its coating, so as to reduce any effect that the injection of this gas can have on the temperature of the substrate and / or the atmosphere in the coating area.

In specially preferred embodiments of the invention, a barrier wall is disposed above the path of the substrate and extending across its entire width, substantially closing the downstream end of the chamber. Such a barrier wall may, for example, be constituted, at least in part, by said discharge shovel if the device is provided with it. It is a very simple way to ensure that changes in conditions immediately downstream from the end of the chamber will not have a direct effect on conditions inside the chamber, and vice versa.

In particularly preferred embodiments of the invention, the processing station is arranged between the outlet from a ribbon forming installation and the inlet of an annealing gallery. When this condition is met, the glass can reach the processing station at a temperature that is, or is close to, that required for the pyrolysis coating reactions to occur. Therefore, the adoption of this characteristic dispenses with the need for another heating device such as that which would be necessary to increase the temperature of the glass to be coated from ambient temperature. It is also important that the coating occurs in a chamber which is physically separate from the tape forming plant on the one hand and the annealing gallery on the other. If such a distinction is not made (and it is common, in the techniques proposed previously in this field, for the coating to be deposited inside the annealing gallery), the atmospheric conditions inside the chamber are then disturbed by gas streams flowing from the annealing gallery and the ribbon forming plant - such streams often cause dust and other pollutants which could become incorporated into the coating, creating defects - and, also, there would be a risk that the profile of the atmospheric currents in the gallery would be disturbed and lead to unfavorable annealing conditions.

In preferred embodiments of the invention, means are present for flowing gas through an inlet slot of the substrate in said chamber from upstream thereof and for preheating this gas, and advantageously the means causing such a gas inlet and / or the shape of the inlet slot are such that they cause a greater flow of such a gas on the edges of the path of the substrate than at its center. The use of a device comprising one or both of these characteristics is advantageous for promoting a general downstream flow of material from the atmosphere inside the chamber and is favorable for conditioning the atmosphere in the area where coating formative material is first deposited on the substrate. For example, it can allow at least partial compensation for the cooling of the atmosphere inside the chamber by contact with its side walls.

A device according to the present invention can advantageously incorporate one or more of the characteristics described in published British patent application No. 2185 249 by the proprietor entitled "Method and device for forming a coating by pyrolysis", which describes and claims a device for the formation by pyrolysis of a coating of metallic compound on the upper face of a hot glass substrate in sheet or ribbon form, comprising transport means for conveying such a substrate downstream along a route, a roof delimiting a chamber open downwards on said route and means for delivering coating formative material into said room, characterized in that, upstream from said room, is an anteroom which communicates with the room via an inlet slit which is partially delimited by the path of the substrate, and via which gas can be brought into the chamber so as to form (during that the device is in operation) a covering which covers the upper face of the substrate along a first part of the length of said chamber, and in that means are present for controllably preheating the gas forming said covering.

The present invention extends to a process for the formation by pyrolysis of a coating of metallic compound on the upper face of a hot glass substrate, this process being carried out optionally, but preferably by means of a device such as described above.

Therefore, the present invention also provides a method of pyrolytically forming a coating of metallic compound on the upper face of a hot glass substrate in sheet or ribbon form during its downstream travel along a path through a chamber in which at least one stream of coating forming solution is sprayed downwards and towards the substrate, characterized in that:

A spraying zone of said chamber is heated to cause the evaporation of a part of the coating forming material before it reaches the substrate and to charge the atmosphere in such a zone of vaporized coating forming material;

The solution is sprayed with sufficient energy to ensure a positive impact of remaining coating-forming material against the substrate to initiate the coating of said face of the substrate, and

- the atmosphere charged with vapor-forming coating material is made to flow downstream from the spraying zone along and in contact with the surface of the substrate being coated for a contact time of 10 seconds at least, and the residue of the current charged with coating formative material is then removed from the substrate.

Such a method allows the formation of coatings having a weak and uniformly weak haze. This is particularly surprising since it has hitherto been believed necessary to remove the vapors of coating formative material and reaction products from the substrate as quickly as possible - contact times between 2 and 5 seconds are used in previously known processes, precisely in order to reduce the risk of harmful deposits, from these vapors, which would lead to an increase in haze.

The reasons why the use of such a process promotes the quality of coatings is not entirely clear. One possible explanation is that a substantial proportion of the thickness of the coating would be made up of vapor-forming coating forming material as the substrate moves through the "passage" portion of the chamber. Vapor deposition techniques are known to promote a fine and uniform crystalline structure of the coating. But this does not explain why the use of a method according to the invention would lead to the formation of a coating which has a thickness far more regular than what can be obtained using conventional methods of phase deposition. steam. Another possible explanation is that, what-

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that only a small proportion of the thickness of the coating is attributable to vapor deposition, there would be conditioning of the newly formed mass of the coating during the contact time of at least 10 seconds during which the substrate is exposed to coating formatter vapor. The crystalline structure of the coating would be affected in a manner favorable to the coating quality and, in particular, the exposure of the freshly formed coating to vapor of coating forming material would allow the filling of small pores thereby forming a coating harder, more compact and resistant to external conditions.

It is possible that part of the explanation is that a favorable crystal structure occurs at the coating / glass interface on contact of the coating forming material with glass when the coating forming material is devoid, or only accompanied a small proportion of solvent. It is believed that the structure of the coating at this interface has a strong influence on how the rest of the coating thickness is made.

It is also possible that the explanation is partially based on less cooling of the glass in the area where the coating is deposited, so that the reactions, which take place while the entire thickness of the coating is formed, produce at a higher and more uniform temperature. This is believed to be favorable for the deposition of a coating of uniform structure, and also tends to increase the coating forming efficiency produced from a given amount of coating formative material. It should be noted here that the speed of the coating reactions increases with temperature, and also that a coating formed at higher temperature generally adheres more firmly to glass than a coating of the same composition, but formed at lower temperature, so it's more durable. In addition, less cooling would imply that there is a lower risk of undesirable thermal stresses in the glass. Such a risk is very real when large amounts of coating forming material solution reach the glass, as required by some prior spray coating techniques, especially when it is desired to form thick coatings on a rapidly moving substrate.

Another theory that could be valid and partially explain the results is that spraying coating formative material through the atmosphere promoting evaporation inside the downwardly opening chamber would cause the area in which the coating forming material first reaches glass is dominated by the continuous supply of fresh reagent and remains free or relatively free of other products.

Preferably, said chamber has a length such that, taking into account the speed of conveying of the substrate, any increment in length of the substrate remains exposed to vapor of coating formative material for at least 20 seconds. This facilitates the formation of thick coatings, for example coatings more than 500 nm thick like those used as protection against infrared radiation. It has surprisingly been found that there is no harmful effect on the quality of the coating formed. Note that, if the coating is deposited between the outlet of a glass ribbon forming installation and an annealing gallery, the tape running speed is governed by the ribbon forming speed, and this will vary depending on the capacity and type of ribbon forming installation, for example if it is a glass drawing machine or a float glass manufacturing installation, and also according to the thickness of the glass that we produce. Since the production speeds of the glass ribbon are usually less than 12 meters per minute, an exposure time of 20 seconds can normally be ensured if the processing station is at least 5 meters long.

In specially preferred embodiments of the invention, said coating forming solution is sprayed from a source located at least 75 cm, and preferably at least 1.2 meters, above said face. substrate. This allows a long delay for the evaporation of these droplets before they reach the substrate and also makes it possible to reduce the intensity with which the current of residual droplets hits the surface of the substrate. In fact, this characteristic itself represents an orientation totally different from that of the previously known proposals. In prior spray coating techniques, coating formative material is sprayed from a location much closer to the substrate, and a spray height of 30 cm or less is usual.

In especially advantageous embodiments of the invention, the vapor-charged atmosphere is extracted from the spraying zone towards a passage formed by a downstream portion of the chamber via a slot of lesser height than the spraying zone. This helps to ensure that the atmosphere laden with coating forming material is concentrated against the substrate, which promotes the coating forming efficiency.

Preferably, the height of said slot is at most equal to half the height between the spray source and said face of substrate. The adoption of this feature leaves at least the upper half of the spraying area for the circulation of gas streams and the upper part of the chamber can form a high density vapor reservoir which feeds the slit continuously.

Preferably, the downstream flow of gas loaded with coating formative material occurs within a passage which is heated. This feature offers several important advantages. Condensation at the ceiling of the passage of coating forming material and / or reaction products which could then drip and soil the substrate is thus prevented, and the coating forming material is kept in the vapor phase. A high temperature can be maintained inside the passage by compensating for at least part of the heat energy removed from the substrate by the coating forming reaction, so that subsequent reactions and conditioning of the already formed coating can occur at a higher temperature, especially towards the downstream end of the passage. This in turn promotes a more uniform crystal structure of the coating and also tends to increase the durability and hardness of the coating.

In particularly advantageous embodiments of the invention, the coating forming solution is sprayed downward and in the downstream direction. This promotes the flow of the sprayed material towards the downstream end of the chamber in which it is sprayed and, at the same time, in comparison with a vertical spraying from the same height, lengthens the path of the current towards the substrate by thus allowing a longer period for the evaporation of the sprayed solution.

Preferably, the coating-forming material and at least one stream of gas are introduced into said spraying zone so that their paths intersect. This arrangement has been found to be particularly advantageous for generating mixing forces within the spraying area thereby ensuring that the vapor of coating formative material is uniformly distributed in the atmosphere which flows downstream from this area along and in contact with the upper face of the substrate.

Advantageously, at least one such stream of gas is discharged from an orifice located in the upper half of the height between the spray source and said substrate face. It has been found to be very effective in promoting such mixing with less disruption of the trajectory of this material near the substrate, which promotes the formation of a high quality coating.

It would be possible to provide heat to the gas discharged into the chamber after it has entered this chamber, but preferably at least one such stream of gas is preheated, since this reduces or eliminates any cooling effect due to this. gas.

In specially preferred embodiments of the invention, at least one such stream of gas is discharged from the upstream side of the path of the pulp coating forming solution.

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verified. This promotes advantageous circulation of the atmosphere within the spray area and tends to reduce any unwanted turbulence.

Advantageously, heat is supplied to said spraying zone at least partially by directing heat radiation downwards from a place situated above the path of the sprayed coating forming solution. This contributes to the evaporation of the sprayed coating formulator solution, especially in the upper regions of its path and on its downstream side, if the solution is sprayed in the downstream direction,

as mentioned above.

In certain preferred embodiments of the invention, on the upstream side of the coating-forming material stream, this stream is protected by a jet of gas which is continuously discharged,

down towards the substrate, in the vicinity of said spray current. This helps to avoid entrainment of any unwanted material, for example reaction products, in the rear part of the stream. The presence of such materials is particularly disadvantageous there, because it can lead to the formation of defects at the substrate / coating interface.

In specially preferred embodiments of the invention, said coating forming material solution is sprayed in the form of a stream of droplets which is repeatedly moved transversely across the path of the substrate. This promotes the mixing of coating formative material evaporated into the atmosphere contained in the spray area of the chamber.

Advantageously, such a jet of protective gas is repetitively displaced transversely to said path, in tandem with the stream of coating formative material. This arrangement offers very effective protection for a given gas introduction rate.

In certain preferred embodiments of the invention, gas is blown upward on each side of the path of the substrate in the spray zone. Such a gas can form screens which serve to protect the side walls of the spray area of the chamber against the corrosive effects of the sprayed material and its reaction products. Such gaseous screens can also prevent the sprayed material, particularly when relatively small amounts are sprayed, from passing below the path of the substrate where it would be available to form an undesirable coating on the underside of a substrate. This undesirable coating may be more or less regular, but so thin that it gives rise to highly detrimental interference effects; for example, it can be more or less regular with a thickness decreasing towards the center of the substrate, or it can be quite irregular with a profile which could recall the marks of a backgammon game.

Material from the atmosphere below the path of the substrate could also tend to flow upward and dilute the vapor concentration of coating formative material especially on the chamber sides. This is undesirable, since it can lead to insufficient deposition from the vapor phase on the edges of the substrate or to insufficient conditioning of the edges coated with such a substrate. Consequently, in particularly advantageous embodiments of the invention, over at least part of the length of the chamber, the flow of material from the atmosphere is prevented beyond the lateral edges of the substrate and between zones located vertically above and vertically below the substrate.

In specially preferred embodiments of the invention, suction forces are generated in a lateral discharge pipe arranged so that material from the atmosphere above the substrate moves away from the central part of the path of the substrate, over at least a portion of the length of said chamber. The adoption of this preferred feature gives advantages which are considered to be particularly important. It promotes good dispersion of the atmosphere charged with vapors of coating-forming material over the entire width of the substrate, thereby increasing the width of the substrate carrying a well-finished coating. In addition, it makes it possible to remove reaction products and excess coating formative material earlier which could become fixed on the coating and contaminate it. It is also useful in removing the reaction products and excess coating formative material before they reach the end of this passage, thereby reducing the risk of corrosion of the walls of the passage. In addition, if the atmosphere below the path of the substrate tends to flow upwards on its sides, this tendency is inhibited in the lateral suction zone. These advantages are favored if, as is preferred, said material is caused to flow laterally from the atmosphere over an area extending over at least the major part of (and preferably substantially over all) the length of said chamber, downstream of the zone of the first deposit of coating material on the substrate.

In certain preferred embodiments of the invention, said material from the atmosphere is extracted by suction at a level located below the substrate. This arrangement is advantageous because it facilitates the finishing of the coating by maintaining a layer of dense vapors of coating formative material against the upper face of the substrate.

Advantageously, gas is discharged into the environment of the substrate so as to form a direct current flowing downstream below each edge of the substrate and along at least part of the length of said chamber.

Surprisingly, it has been found that the adoption of this preferred characteristic results in significantly clarifying the atmosphere which would be in contact with the glass before it enters the room, so that there is a considerable reduction. the quantity of pollutants capable of forming harmful deposits on the glass before it is coated. The adoption of this preferred feature of the invention also offers certain very important advantages in reducing the risk of coating formation on the underside, which contributes to the quality of the product formed. Advantageously, such a gas stream flows below the substrate over the entire width of the substrate. The adoption of this characteristic promotes the clarification of the atmosphere below the path of the substrate in a very efficient manner and thus avoids harmful premature deposits of material which has been entrained in back currents flowing below the substrate in the upstream direction.

Preferably, the gas to be discharged to form such a current below the level of the substrate is preheated to about fifty degrees Celsius of the average temperature of the substrate im-45 just before its coating, so as to reduce any effect that the injection of this gas can affect the temperature of the substrate and / or the atmosphere in the coating area.

In specially preferred embodiments of the invention, the chamber is substantially closed at its downstream end 50 to prevent the exchange of material from the atmosphere between the downstream end of the chamber and another region further down the route of the substrate. Such a closure can, for example, be carried out by the evacuation pipe extending over the entire width of the chamber at its downstream end. The adoption of this characteristic has the advantage of avoiding the dilution or pollution of the atmosphere at the downstream end of the chamber by the atmosphere of the region located further downstream, and it also prevents currents of the atmosphere in the chamber does interfere with further processing of the substrate and the deposition of unwanted additional material on the coating. In particularly advantageous embodiments of the invention, the glass substrate is a ribbon of freshly formed hot glass and the coating is formed after this ribbon leaves a forming installation and before it enters an annealing gallery. The chamber can therefore be arranged in a location where the glass 65 is at a temperature suitable for the pyrolysis coating reactions to occur, so that costs incurred by reheating the glass to such a temperature are avoided or substantially reduced. It is also important that the coating

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occur in a room that is physically separate from the ribbon forming plant on the one hand and the annealing gallery on the other. If such a distinction is not made (and it is common, in the techniques proposed previously in this field, for the coating to be deposited inside the length 5 of the annealing gallery), the atmospheric conditions of the chamber are then disturbed by gas currents flowing from the annealing gallery and the ribbon forming plant - such currents often cause dust and other pollutants which could become incorporated in the coating, creating of 10

faults - and there would also be a risk that the profile of atmospheric currents in the gallery would be disturbed and lead to unfavorable annealing conditions.

In particularly preferred embodiments of the invention, preheated gas is introduced and it is made to flow downstream into said chamber in contact with the substrate. The adoption of this characteristic is advantageous, because it promotes a general downstream flow of material from the atmosphere inside the chamber and favorably conditions the atmosphere in the area where coating forming material is deposited for the first time on the substrate. For example, in some of these preferred embodiments of the invention, a greater volume flow rate of preheated gas is brought into and flowed into the chamber at the edges of the substrate than at its center. This allows at least partial compensation for the cooling of the atmosphere inside the chamber by contact with its side walls.

In fact, the present invention can advantageously be combined with the invention described in the published British patent application No. 2185 249 of the proprietor entitled "Method and device for forming a coating of glass by pyrolysis", which describes and re - 30 vendique a pyrolytic coating process in which a hot sheet or ribbon-like glass substrate moves in a downstream direction below an open chamber down on the substrate and in which a coating is formed on the upper face of said substrate from coating formative material, characterized in that the gaseous atmosphere in the immediate vicinity of the upper face of the substrate, at least in the zone where the formation of the coating begins, is controlled by introducing in the downstream direction, in said chamber, of the preheated gas which enters the chamber in contact with the substrate and forms a cover which covers the substrate at least along its length of this area.

The present invention is particularly suitable for forming coatings with a high growth rate, for example greater than 20 nm / second, as is for example the case for forming relatively thick coatings, such as coatings from 45,500 nm to 1000 nm thick, on a freshly formed glass ribbon moving several meters per minute from a float tank or other flat glass forming installation.

A particularly important use of a process according to the invention is the formation of tin oxide coatings from stannous chloro-rare as a coating-forming material. Tin oxide coatings, which reduce the emissivity to long wavelength infrared radiation from the glass sheet surfaces on which they are deposited, are widely used to reduce heat transmission from 55 glazed structures. This is obviously only an example of the use of the process. As another example, the process can be used to form a coating of titanium dioxide or a mixture of oxides such as a mixture of cobalt, iron and chromium oxides.

The invention will now be described in more detail with reference to the appended schematic drawings which represent different embodiments of devices according to the invention and by examples of specific methods according to the invention implemented by means of such devices.

In the drawings, each of FIGS. 1 to 4 is a side view in section 65 of an embodiment of the coating devices according to the invention, and FIG. 5 is a section along the line V-V of FIG. 2.

Figure 1

In FIG. 1, a device for the formation by pyrolysis of a coating of metallic compound on the upper face of a hot glass substrate 1 in the form of a sheet or a ribbon comprises transport means such as rollers 2 for conveying such a substrate in the downstream direction 3 along a path also indicated by the reference numeral 1. The path 1 crosses a treatment station 4 comprising a roof 5 delimiting a chamber 6 opening downwards on the path of the substrate 1, and a spray nozzle shown diagrammatically at 7 sprays a spray of coating formulator solution into the chamber 6, in a direction 8 oriented downward towards the substrate.

The spray nozzle 7 is arranged so as to spray the stream of coating forming material solution in a spraying area 9 of the chamber 6 from a location situated at a height of at least 75 cm above the path of the substrate. 1. In the illustrated embodiment, the spray nozzle 7 is arranged to spray coating formative material from at least 1 meter, and preferably at least 1.2 meters, above the path of the substrate 1, and it is of a type well known per se. The nozzle is arranged to spray the coating forming material solution in the direction 8 facing downwards on the substrate 1 and in the downstream direction 3, and it is movable back and forth along a track (not shown) transverse to the path of the substrate.

Heating means are provided to provide heat to said spray area. In the illustrated embodiment, such heating means comprise radiant elements 10 directed downwards and arranged in the roof of the spraying zone 9. As additional heating means, a pipe 11 emits a stream of preheated gas in the spraying area in a direction which intersects the stream of sprayed coating formative material. The blowing orifice 12 of the pipe 11 is disposed in the upper half of the height between the spray nozzle 7 and the substrate 1, and is arranged so as to blow this gas stream from a position located upstream of the unloading axis 8 of the sprayed spray of coating forming material. The orifice 12 extends horizontally over the entire width of the path of the substrate 1, and vertically over the upper third of the height of the spray nozzle 7 above the glass substrate. The gas emitted by the orifice 12 is initially directed substantially horizontally, through the transverse path of the stream of droplets 7, to maintain a circulation of gas inside the spraying zone 9.

The blown gas is preferably preheated, for example to an average temperature between 300 ° C and 500 ° C. The heating elements 10 promote the evaporation of the solvent from the sprayed droplets during their journey to the substrate 1, and this solvent can then be entrained in the hot gas discharged.

In an optional alternative embodiment, the pipe 11 is divided into two conduits ending in an upper orifice and a lower orifice of the same dimensions occupying the position of the orifice 12, so that gas streams at different temperatures , for example 300 ° C and 500 ° C, can be emitted at different levels.

The roof 5 delimits a passage from the chamber 6 leading downstream from the spraying zone 9 and giving the chamber 6 a total length of at least 2 meters, and preferably a length of at least 5 meters. In the illustrated embodiment, the roof 5 has a barrier wall 14 above the path of the substrate which descends substantially vertically to delimit an outlet slot 15 at the downstream end of the spraying zone and which separates this zone from the passage, and the passage 13 has a height substantially equal to that of the spraying zone 9. The height of the outlet slot 15 is less than half the height between the spray nozzle 7 and the substrate 1.

Upstream of the discharge axis 8 of the spray nozzle for the coating forming material is a nozzle

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gas distribution shown schematically at 16 which emits a gas jet downwards in the vicinity of the stream of coating formative material to protect the sprayed coating formative material. The gas-emitting nozzle 16 is integral with the spray nozzle 7, so that they move simultaneously back and forth along the transverse track. A main effect of this protective gas stream is to avoid entrainment of coating reaction products and other pollutants behind the stream 7 of coating forming material during its path to the uncoated surface of the substrate. 1.

Evacuation pipes 17,18,19 are arranged along the passage 13, which is high, and the evacuation pipe 17 at the downstream end of the chamber has an inlet orifice 20 disposed above the course of the substrate which extends over at least most of its width. Deflectors such as 21 stand up from the side walls of the chamber 6 to prevent the flow of material from the atmosphere beyond the edges of the path of the substrate and between zones situated vertically above and vertically below this path, along the length of the spraying zone 9, where the atmosphere will be richer in coating formative material. These deflectors can be mounted on pivots on the side walls of the chamber 6 and be supported for example by threaded rods, so as to be able to adjust their position to minimize their spacing with respect to the edge of the substrate 1.

Means 22 are present for discharging gas into the environment of the substrate 1 so as to form a direct current flowing in the downstream direction 3 below each edge of the path of the substrate 1 and over at least part of the length of the route occupied by room 6.

The gas blowing means below the ribbon comprise four boxes 23 arranged in pairs and extending through substantially the entire width of the chamber 4. At the top of each box 23 is a slot 24 bordered by a deflecting lip 25, so that the gas injected through the slots 24 is directed in the downstream direction 3 along the treatment station 4. The slots 24 extend over the entire length of the boxes 23 through the station treatment 4. If desired, such slots may be replaced by several spaced orifices. As shown in FIG. 1, a deflector plate 26 is disposed above the boxes 23, so that the injected gas is not blown directly against the substrate 1. The boxes 23 can be supplied with preheated gas from both sides of the treatment station, for example from heat exchangers. The blown gas can be air, and this can be easily heated by heat exchange with burnt oven gases. Such a gas is preferably preheated to around fifty degrees Celsius of the temperature of the substrate when the latter enters the chamber 6.

The gas discharged below the substrate 1 can be removed from the atmosphere of the substrate 1 by an optional evacuation pipe (not shown) having one or more inlets extending transversely below the path of the substrate, arranged for example at right of the upper discharge inlet 20. A barrier partition 27 is disposed above the path of the substrate 1, extends over the entire width of the downstream end of the chamber 6 and substantially closes it, so as to substantially avoid the flow of material from the atmosphere into or out of the chamber at the downstream end of passage 13.

The treatment station 4 is arranged between the outlet from a ribbon forming installation (not shown), for example a float tank, and the inlet from an annealing gallery 28.

A passage between the ribbon forming installation and the chamber 6 has a roof 29, and the upstream end of the chamber is determined by a dam 30 descending from the roof of the passage 29 and leaving little day for the passage via a slot inlet 31 of the substrate 1 in the chamber.

The effect of this barrier 30 is to limit the entry of material from the atmosphere into the chamber 6 from upstream, so that the atmospheric conditions inside this region can be more easily controlled.

Upstream of the dam 30, between the latter and a second partition 32, there is an anteroom 33 in which are arranged heating elements 34 to preheat any gas drawn into the chamber 6 between the dam 30 and the strip 1.

Example 1

In a specific practical embodiment of the device shown in Figure 1, the chamber 6 is a little more than 3 meters wide, so as to treat glass ribbons of width up to 3 meters. The roof 5 above the spray zone 9 of the chamber is just 1.5 meters above the level of the path of the tape 1, and the spray droplet orifice of the nozzle 7 is close to the level from this roof. This nozzle 7 is arranged so as to discharge a conical stream of droplets with a conical half-angle of 10 ° and along an axis 8 making an angle of 47 ° on the horizontal; the gas discharge nozzle 16 has its orifice 25 cm below and 7 cm downstream from the spray nozzle, and its axis is 60 ° on the horizontal. The gas blowing orifice 12 has 50 cm high and its top is at the level of the nozzle 7. The wall 14 at the downstream end of the spraying zone is separated from the orifice 12 emitting a gas stream from a distance of 2.8 meters. The passage 13 has the same height as the spraying zone 9 and the outlet slot 15 has a height of 50 cm above the level of the path of the tape 1. The length of this passage is 4 meters.

This device is particularly intended for the deposition of tin oxide coatings from a stannous chloride solution as a coating forming material.

Using such a device, a coating of tin oxide 750 nm thick is formed on a 6 mm thick glass ribbon moving at a speed of 8.5 m / min. The glass entering the chamber has a temperature of 600 ° C, and the coating forming material used is an aqueous solution of stannous chloride containing ammonium bifluoride to provide doping ions to the coating. This solution is sprayed at the rate of 2201 / h, while the nozzle is driven back and forth through the path of the tape at the rate of 22 cycles per minute.

The anteroom 33 is substantially closed and the atmosphere therein is heated by electric heating resistors.

Radiant heating elements located in the roof of the spraying area are turned on and gas is blown through the orifice 12 at a rate of 7000 Nm3 / min and at a temperature of 400 ° C. Gas is emitted from the chambers 23 below tape at a temperature of 600 ° C.

While the operation is in progress, it has been noted that by the time the stream of sprayed coating formative material reaches the ribbon level, a substantial proportion of solvent has evaporated from the stream, leaving very small droplets of stannous chloride liquid and stannous chloride vapor to contact the glass and begin the formation of the coating. The spray zone 9 above the ribbon is filled with a circulating atmosphere charged with stannous chloride vapor, and this is attracted through the outlet slot 15 in the passage 13 by generated suction forces. in the discharge pipe 17, 18, 19. The atmosphere inside the chamber has been found to be substantially clear, except in the vicinity of the stream of droplets, which indicates that substantially all of the stannous chloride and solvent out of this stream is in the vapor phase, so that over most of the length of chamber 6 in which the glass is exposed to coating formative material, the atmosphere in this chamber 6 is substantially free of matter in liquid phase. Obviously, passage 13 also contains reaction products. The forces generated and the geometry of this passage are such that the material of the atmosphere leaving the exit slit 15 slows down and that fairly dense vapors of chloride

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stannous tend to form a layer in contact with the coating being formed to allow the conditioning of this coating, while the less dense solvent vapors and reaction products tend to flow more directly to the drain. It follows from all of this that the coating formed has a fine crystal structure at the glass / coating interface which promotes a uniform structure and therefore a coating of high quality and having good optical qualities, and the inclusion of reaction products which would lead to faults tends to be avoided.

It should be particularly noted that the haze shown by the glass carrying the coating is very weak and very uniform.

Figures 2 and 5

In FIGS. 2 and 5, the elements serving functions similar to those illustrated in FIG. I have received the corresponding reference numbers.

In the spraying zone 9 at the upstream end of the chamber 6, the gas discharge pipe 11 is absent, but is replaced by a pair of conduits 35 having orifices 36 which are directed towards each other to discharging preheated gas from opposite sides of the axis 8 of the sprayed coating form material. No other means of heating the chamber is present above the level of the ribbon I. The orifices 36 extend over almost the entire width of the chamber 6 and they are arranged in the upper third of the height of the spray nozzle 7 above the substrate. In a variant, the orifices 36 have a narrower width and are moved back and forth through the spraying zone in tandem with the spraying nozzle 7.

On the downstream side of the spraying area 9, the roof 5 is inclined downward and then forms a vertical wall 14 in which is disposed over its entire width an inlet 37 of an evacuation pipe 38 for the suction of vapors from the spray area, so as to avoid stagnation inside this area.

Downstream of the outlet slot 15 below the wall 14, the roof extends and delimits a passage portion 13 of the chamber 6 which has the same height as the outlet slot.

Over the length of this passage 13, evacuation means are present on each side of the chamber, below the level of the path of the substrate 1. These evacuation means comprise several evacuation boxes 39 open at their top and communicating with lateral evacuation pipes 40. In FIG. 2, it will be noted that these evacuation boxes 39 extend over the entire length of the path of the substrate occupied by the passage 13, and that the upstream evacuation box is in fact arranged below the spraying area 9. Deflectors 41 projecting upward and inward drainage boxes extend below the edges of the path of the substrate and upward between the rollers of conveyor 2. This arrangement provides effective separation of the atmospheres vertically above and vertically below the path of the substrate along the passage.

In order to prevent coating formative material and material from the atmosphere from flowing beyond the edges of the path of the substrate in a region further upstream of the spraying zone 9, fans 50 are available. which blow preheated air so as to maintain an upward flow of relatively clean gas against the side walls of the chamber. This also gives a certain degree of protection of these walls against corrosion due to the atmosphere inside the chamber.

Example 2

The device of Figure 2 is used to form a coating of the same thickness as in Example 1 using the same coating forming material and on a glass ribbon of the same thickness which moves at the same speed. The spray nozzle 7 is also controlled, as in Example 1. The chamber has a total length of 7.5 meters.

The glass enters chamber 6 at a temperature of 600 ° C. and air preheated to 500 ° C. is discharged at the rate of 3600 Nm 3 / h through each of the orifices 36. It follows that a major part of the solution spray is evaporated on its way to the ribbon, while a residual current continues and positively meets the glass.

The suction, below the level of the path of the substrate, of material from the atmosphere along the passage tends to maintain at the bottom thereof a layer of atmosphere charged with vapor of coating-forming material, in contact with the tape, to promote the finish of the coating. The total suction extracts around 70,000 Nm3 / h at an average temperature of 350 ° C.

This also gives excellent results with regard to the uniform high quality of the coating formed, especially with regard to the level of haze which is low and uniformly low.

Figure 3

In FIG. 3, the elements serving functions similar to those illustrated in FIGS. 1 and 2 have been given the corresponding reference numbers.

The spraying zone 9 is similar in shape to that shown in FIG. 1 but, in FIG. 3, means for introducing preheated gas into this zone include an unloading pipe 42 terminating in several gas outlet orifices in the roof 5 of the room and distributed over most of its surface. The movement path of the spray nozzle 7 runs along an upstream end wall 43 of the chamber.

Below this upstream end wall 43, the dam 30 of FIGS. 1 and 2 is replaced by a bridge 44 allowing a higher entry slit 31, so that atmospheric matter can be more easily drawn from the anteroom 33 towards the interior of the chamber in contact with the glass. If desired, the bridge 44 can be adjustable in height to modify the opening of the inlet slot 31. An additional gas discharge pipe 45 is present to discharge preheated gas down into the anteroom, from so as to control the atmosphere layer situated immediately above the substrate 1 at least up to the zone where the flow of coating formative material 8 reaches the glass.

This embodiment of the present invention therefore uses the invention described and claimed in our published British patent application No. 2185 249, entitled "Method and device for forming a glass coating by pyrolysis".

As in Figure 2, the passage has the same height as the exit slot of the spraying area.

At the downstream end of the passage 13, material from the atmosphere is sucked into the discharge pipe 46 having an inlet 47 delimited in part by a curved discharge shovel 48 which extends above the course of the substrate 1 over the entire width of the passage and substantially closes its downstream end. Such a shovel 48 can, as a variant, be mounted on a pivot so as to be able to adjust its position to obtain a minimum day with the substrate 1. Also at the downstream end of the passage 13, material from the atmosphere is sucked into an evacuation pipe 49 disposed on each side of the chamber, in order to promote lateral dispersion of the material of the atmosphere flowing along the chamber. Such material is also prevented from flowing below the substrate by means of deflectors such as 21 projecting from the side walls of the chamber above the margins of the substrate substantially along the entire length of the passage and extending into the spray area, almost to its upstream end.

Example 3

The device of FIG. 3 is used to form a coating of a mixture of titanium dioxide and ferric oxide on sheets of glass 5 mm thick moving at a speed of 10 m / min, using a titanium acetylacetonate starting solution and

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iron (III) acetylacetonate. Glass enters the room at a temperature of 580 ° C and this room is 6 meters long.

The solution is sprayed at a rate of approximately 80 l / h at a pressure of approximately 25 bar, in order to obtain a coating 45 nm thick; this coating is yellowish and very reflective. The spray nozzle is placed at a height of 1.2 meters above the tape inclined 30 ° horizontally, and is moved back and forth across the path of the substrate at the right rate. 20 cycles per minute.

Air preheated to a temperature of 350 ° C is blown through the roof of the spraying area at a rate of approximately 1500 Nm3 / h, and air preheated to a temperature of 580 ° C is blown to the low in the anteroom 33 at about 3000 Nm3 / h. Part of the sprayed current is evaporated before reaching the glass, and part continues and strikes the glass positively.

The suction flow to the downstream evacuation pipe 46, 49 is adjusted so as to compensate for the total amount of gas blown or drawn into the chamber, taking account of the creation of gas inside the chamber, creation due to evaporation of the sprayed material.

The process results in the formation of a very uniform and substantially flawless coating.

Figure 4

As before, the elements serving functions similar to those illustrated in the previous figures have again received the corresponding reference numbers.

In the embodiment of Figure 4, the single spray nozzle reciprocating from the previous figures is replaced by several nozzles of this type, although only one is shown. These nozzles 7 are moved on portions of tracks (not shown) located between two gas discharge pipes 35 having orifices 51 inclined downward extending over the entire width of the chamber.

The roof 5 descends in a partially curved continuous shape above the spraying zone 9 and it continues to descend, so that the passage 13 has a decreasing height in the downstream direction, facilitating a regular flow of material towards the downstream inside the chamber 6. As in FIG. 3, lateral evacuation pipes are present for sucking, from this passage, material from the atmosphere at its downstream end, but, in this figure, these vacuum cleaners occupy a little more than half the length of the passage. The slope of the roof of the passage compensates for the reduced quantity of material flowing along the passage, reduction due to this increase in suction.

At the upstream end of the chamber, the end wall 43

descends near the substrate path 1, substantially closing this end of the chamber, and just downstream of this end partition is disposed an auxiliary gas blowing duct 52 which emits preheated gas into the chamber adjacent to the substrate . This gas flows in the upstream direction, to condition the atmosphere in contact with the substrate, where it is reached for the first time by the coating forming material, and to prevent the accumulation of vapor against the wall of upstream end 43.

At the downstream end of the spraying area, two gas discharge orifices 53, directed horizontally and inclined inwards, are arranged so as to entrain the vapor of coating formative material, which will be generated inside. from the spray area, inward in the downstream direction, away from the side walls of the passage.

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Example 4

A 40 nm thick fluorine doped tin oxide coating is formed on a 4 nm thick glass ribbon moving from a float chamber at a speed of 8.5 m / min and penetrating in the room at a temperature of 600 ° C. The room has a total length of 8 meters.

The coating forming material used is an aqueous solution of stannous chloride containing ammonium bifluoride to provide doping ions to the coating. This solution is sprayed through the nozzles at the rate of 1101 / h. The nozzles are all parallel and inclined by 75 ° on the horizontal. They are arranged 1.5 meters above the substrate.

Air preheated to 550 ° C is discharged at a rate of 5000 Nm3 / h 30 through the two orifices 51 to entrain solution of evaporated coating formatter, and the air blown through the auxiliary duct 52 is also preheated to 500 ° C. The suction above the level of the substrate is controlled so as to compensate for the quantity of gas introduced or formed in the chamber and to favor a general flow of material downstream.

Air preheated to 600 ° C is discharged at the rate of 3000 Nm3 / h by the blowing means 22 below the path of the substrate.

This process also results in the formation of a very uniform coating, substantially free of local defects and having a very low and uniformly low haze.

Examples 5 to 8

In a variation of each of the above examples, the illustrated device is used to form a coating on glass which has been cut into sheets and then reheated, by methods at all other points as described.

Similar results are obtained.

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2 sheets of drawings

Claims (57)

670,447 2 1. Device for the formation by pyrolysis of a coating of metallic compound on the upper face of a hot glass substrate in sheet or ribbon form, comprising transport means for conveying such a substrate downstream along of a route, a treatment station comprising a roof delimiting a chamber open downwards on said route and means for spraying a coating forming solution in said chamber, downwards and in the direction of the substrate, characterized in that: - The spraying means are arranged so as to spray said coating forming solution in a spraying zone of said chamber from a height of at least 75 cm above the path of the substrate; - Heating means are present and supply heat to said spraying zone; The whole delimits a portion of said chamber forming a passage downstream from said spraying zone and giving the chamber a total length of at least 2 meters, and - Means are present for generating suction forces acting on the atmosphere located inside the passage by promoting the flow of the material which constitutes it along the path of the substrate towards the downstream end of said passage and the penetration of the latter into an evacuation pipe which separates it from the path of the substrate. 2. Device according to claim 1, characterized in that the chamber has a length of at least 5 meters. 3. Device according to one of claims 1 or 2, characterized in that the spraying means are arranged so as to spray said coating forming solution from a source located at least 1 meter, and preferably at least 1, 2 meters, above the substrate path. 4. Device according to one of claims 1 to 3, characterized in that, at the downstream end of the spraying zone, the whole descends substantially vertically to delimit an outlet slot leading to said passage. 5. Device according to claim 4, characterized in that the height of said outlet slot is at most equal to half the height between the spray source and the path of the substrate. 6. Device according to one of claims 1 to 5, characterized in that, over at least part of its length, the passage has a height less than that of the spraying zone. 7. Device according to one of claims 1 to 6, characterized in that the roof converges downstream towards the path of the substrate over the length of said passage. 8. Device according to one of claims 1 to 6, characterized in that the roof comprises a bridge over the path of the substrate which delimits an outlet slot of the spraying zone and which separates this zone from said passage, this passage having a height greater than that of the exit slot. 9. Device according to one of claims 1 to 8, characterized in that the spraying means are arranged so as to spray the coating forming material downwards and in the downstream direction. 10. Device according to one of claims 1 to 9, characterized in that means are present for delivering coating formative material and at least one gas stream in said spraying zone in directions which intersect. 11. Device according to claim 10, characterized in that it comprises at least one device for delivering gas having an orifice disposed in the upper half of the height between the spray source and said substrate face. 12. Device according to one of claims 10 or 11, characterized in that means are present for preheating at least one such stream of gas. 13. Device according to one of claims 10 to 12, characterized in that at least one device for delivering gas is arranged so as to discharge such a stream of gas from a location located upstream of the spray axis of coating formative material. 14. Device according to one of claims 1 to 13, characterized in that downward-directed radiation heating means are placed above the spraying zone. 15. Device according to one of claims 1 to 14, characterized in that means are present for heating said passage from above. 16. Device according to one of claims 1 to 15, characterized in that, upstream of the spraying axis of the spraying means of the coating forming material, means are present for discharging a gas jet downwards in the vicinity of said spray axis, so as to protect from the sprayed coating forming material. 17. Device according to one of claims 1 to 16, characterized in that the means for spraying coating forming material comprise a spray nozzle and means for repetitively moving such a nozzle along a path transverse to the substrate path. 18. Device according to one of claims 16 or 17, characterized in that means are present for repetitively moving such means for discharging a jet of protective gas along a path transverse to said path of the substrate in tandem with the spray of coating formative material. 19. Device according to one of claims 1 to 18, characterized in that means are present for blowing gas upwards on each side of the path of the substrate in the spraying zone. 20. Device according to one of claims 1 to 19, characterized in that an evacuation pipe is arranged at the downstream end of said chamber and has one or more inlets arranged above the path of the substrate and s' extending across at least most of its width. 21. Device according to claim 20, characterized in that a curved shovel is present at such a discharge inlet. 22. Device according to one of claims 1 to 21, characterized in that means are present to prevent the flow of material from the atmosphere beyond the sides of the path of the substrate and between zones situated vertically above and vertically below this path, over at least part of the length of the chamber. 21. Device according to claim 22, characterized in that such means for preventing the flow comprise deflectors. 24. Device according to one of claims 1 to 23, characterized in that means are present for generating suction forces in a lateral evacuation pipe arranged so as to make the material move away from the atmosphere. surmounting the path of the substrate from the center of said path, over at least a portion of said passage. 25. Device according to claim 24, characterized in that said discharge pipe is arranged so as to suck material from the atmosphere, laterally, over an area extending substantially over the whole of said passage. 26. Device according to one of claims 24 or 25, characterized in that said lateral evacuation pipe has inlets which are arranged below the level of the path of the substrate. 27. Device according to one of claims 1 to 26, characterized in that means are present for discharging gas into the environment of the substrate, so as to form a direct current flowing downstream below each edge of the path of the substrate and along at least part of the length of the path occupied by said chamber. 28. Device according to claim 27, characterized in that the means for discharging gas to form such a current in 5 10 15 20 25 30 35 40 45 50 55 60 65 3 670,447 below the level of the path are arranged so as to discharge gas to form such a current through the total width of the path of the substrate. 29. Device according to one of claims 1 to 28, characterized in that a barrier wall is disposed above the path of the substrate by extending across its entire width and substantially closing the end downstream of said chamber. 30. Device according to one of claims 1 to 29, characterized in that the treatment station is arranged between the outlet of a ribbon forming installation and the inlet of an annealing gallery. 31. Device according to one of claims 1 to 30, characterized in that means are present for flowing gas through an entry slit of the substrate in said chamber from upstream thereof and to preheat this gas. 32. Device according to claim 31, characterized in that the means causing such an entry of gas and / or the shape of the inlet slot are such that they cause a greater flow of such a gas on the edges of the path of the substrate only at its center. 33. A method of actuating the device according to claim 1 for the formation by pyrolysis of a coating of metallic compound on the upper face of a hot glass substrate in the form of a sheet or ribbon during its downstream transport. along a path through a chamber in which at least one stream of coating forming solution is sprayed downward and towards the substrate, characterized in that: A spraying zone of said chamber is heated to cause the evaporation of a part of the coating forming material before it reaches the substrate and to charge the atmosphere in such a zone of vaporized coating forming material; The solution is sprayed with sufficient energy to ensure a positive impact of remaining coating-forming material against the substrate to initiate the coating of said substrate face, and - the atmosphere laden with vapor-forming coating material is made to flow downstream from the spraying zone along and in contact with the surface of the substrate being coated for a contact time of 20 seconds at least, and the residue of the current charged with coating formative material is then removed from the substrate. 34. Method according to claim 33, characterized in that any increment in length of the substrate is exposed to vapor of coating formative material for at least 20 seconds. 35. Method according to one of claims 33 or 34, characterized in that said coating forming solution is sprayed from a source located at least 75 cm, and preferably at least 1.2 meters, au- above said substrate face. 36. Method according to one of claims 33 to 35, characterized in that the vapor-charged atmosphere is extracted from the spraying zone towards a passage formed by a downstream portion of the chamber via an outlet slot of lesser height than the spray area. 37. Method according to one of claims 33 to 36, characterized in that said downstream flow of gas loaded with coating formative material occurs inside a passage which is heated. 38. Method according to one of claims 33 to 37, characterized in that the coating forming solution is sprayed downward and in the downstream direction. 39. Method according to one of claims 33 to 38, characterized in that the coating-forming material and at least one stream of gas are introduced into said spraying zone so that their paths intersect. 40. The method of claim 39, characterized in that at least one such stream of gas is discharged from an orifice located in the upper half of the height between the spray source and said substrate face. 41. Method according to one of claims 39 or 40, characterized in that at least one such stream of gas is preheated. 42. Method according to one of claims 39 to 41, characterized in that at least one such stream of gas is discharged from the upstream side of the path of the sprayed coating forming solution. 43. Method according to one of claims 33 to 42, characterized in that heat is supplied to said spraying zone at least partially by directing heat radiation downwards from a place situated above the path of the solution spray coating trainer. 44. Method according to one of claims 33 to 43, characterized in that, on the upstream side of the coating-forming material stream, this stream is protected by a gas jet which is discharged continuously, downwards towards the substrate, in the vicinity of said sprayed current. 45. Method according to one of claims 33 to 44, characterized in that said solution of coating forming material is sprayed in the form of a stream of droplets which is repeatedly displaced transversely across the path of the substrate. 46. A method according to claims 44 and 45, characterized in that such a jet of protective gas is repetitively displaced transversely to said path, in tandem with the stream of coating formative material. 47. Method according to one of claims 33 to 46, characterized in that gas is blown upwards on each side of the path of the substrate in the spraying zone. 48. Method according to one of claims 33 to 47, characterized in that, over at least part of the length of the chamber, the flow of material from the atmosphere is prevented beyond the lateral edges of the substrate and between areas located vertically above and vertically below the substrate. 49. Method according to one of claims 31 to 48, characterized in that suction forces are generated in a lateral evacuation pipe arranged so that material from the atmosphere above the substrate moves away from the central part of the path of the substrate, over at least a portion of the length of said chamber. 50. Method according to claim 49, characterized in that said material flows from the atmosphere laterally, over an area extending at least over most of the length of said chamber, downstream of the area of the first deposit on the coating material substrate. 51. Method according to one of claims 49 or 50, characterized in that said material from the atmosphere is extracted by suction at a level located below the substrate. 52. Method according to one of claims 33 to 51, characterized in that gas is discharged into the environment of the substrate so as to form a direct current flowing downstream below each edge of the substrate and the along at least part of the length of said chamber. 53. The method of claim 52, characterized in that such a gas stream flows below the substrate under the entire width of the substrate. 54. Method according to one of claims 33 to 53, characterized in that the exchange of material from the atmosphere between the downstream end of the chamber and another region further downstream of the path of the substrate is prevented by closing substantially the downstream end of the chamber. 55. Method according to claim 54, characterized in that the glass substrate is a freshly formed ribbon of hot glass and the coating is formed after this ribbon has left a forming installation, and before it enters an annealing gallery. 56. Method according to one of claims 33 to 55, characterized in that the preheated gas enters and flows downstream into said chamber in contact with the substrate. 57. Method according to claim 56, characterized in that such a preheated gas is penetrated into said chamber at a higher volume flow rate on the edges of the substrate than at its center. 5 10 15 20 25 30 35 40 45 50 55 60 65 670,447 4